Moving a gas water heater into the envelope of the home…or switch to electric?
Benneaf
| Posted in Mechanicals on
I just acquired a early 90’s home and it turns out we can’t get our minivans into the garage! On one side we have the HVAC equipment and on the other the water heater (both are gas). The HVAC I think we can relocate to an area of the bonus room directly over the garage so there will be minimal adjustment needed to the duct work. The logical place to relocate the water heater will be just inside on the same wall it is now which is currently a laundry room. I have never had a house with gas units inside the envelope of the home. So…. If I stay with gas what do I need to make sure happens with venting, etc to stay safe? Thanks
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Replies
Andrew,
In the past, atmospherically vented gas water heaters (the type with a flue that includes a fitting that looks like an upside-down funnel with air leaks at the sides) were routinely installed indoors -- usually in a basement, but often in a mechanical room. With today's tighter houses, however, most experts recommend against this practice. (The danger is that an atmospherically vented water heater is at risk of backdrafting -- also called spillage. This occurs when an exhaust fan -- for example, a range hood fan -- depressurizes the house, pulling exhaust gases down the water heater flue and into the house.)
If you want to install a gas water heater indoors, it's best to verify that it's a sealed-combustion model (that is, one with two pipes leading outdoors: a flue pipe and an air-intake pipe). Otherwise, choose an electric water heater (either an electric resistance model or a heat-pump water heater).
What about the gas pack heat system? Same thing?
Andrew,
If I understand correctly, a gas pack unit -- a combination air conditioner/gas furnace -- is always installed outdoors. So the concerns you raise don't apply.
hmmm...maybe I don't have a gas pack. I have a thing with flames in it in the garage that is connected to a bunch of duct work...and what looks like a traditional whach-a-ma-call-it with (probably) a compressor inside it outside...on the other side of the house.
Andrew,
If the equipment you are looking at is designed to provide cooling, it is called an air handler.
If the equipment you are looking at is designed to provide heat, it is either a furnace (if the fuel is natural gas, propane, or fuel oil) or an air handler connected to a heat pump (if the fuel is electricity).
If the water heater is the original from the 90s, or a replacement getting on in age don't even think about moving it- scrap it.
To figure out sealed combustion gas vs. electric:
What are your full-retail utility rates? (Take the whole power bill, divide the $ /kwh. Similarly, with the gas bill.)
How many occupants, and the volume of the biggest tub you need to fill?
Andrew ,
Where is this house and if it is not already well insulated and air sealed are these things you intend to do in the future ? Regardless of the answer to this question you want whatever you install to obtain it's makeup air from the outdoors and you'll need to verify that this is done when installation takes place . too many guys I see just do not pipe the intake to the outdoors and let it draw from the interior .
Here's what I am hearing...if I move it inside the envelope make sure the units are "sealed" or that they draw intake air from the exterior. As old as they are...both look original...its pretty much guaranteed the aren't. So if I have to move them, then I should just replace them....does that sum it up?
Richard, the house is in east TN. It does not appear to be well insulated or well sealed. I'll do what I can, but I am not ripping out sheetrock or tearing off siding to do a deep energy retrofit. I will seal up, insulate, and probably dehum the crawl space, and do a bit with the windows where I can. That would mean either a good quality storm window or a acrylic window liner.
Dana, here in TVA land power is cheap. Off the top of my head I think we are around 10 cents a KW for electric. Gas is less, but the equipment is more and it is doubtfull we will be in the house more than 2-3 years. I'll double check the rates, but I am thinking that would point me to electric.
If you're looking at 2-3 year time frame, a cheap electric tank sized to be able to fill the tubbie works. If you were looking at a longer time frame and the laundry room was sized adequately and the additional noise were not an issue, a heat pump water heater could still have a rationale, even with 10 cent electricity, but it's doubtful that you'd ever recoup the upfront cost in a resale.
Even though they cost more up front, low-E storm windows have a faster payback than clear-glass, and are more comfortable too. It'll pay the cost difference for the low-E glass in 2-3 years, if not the entire window. The Larson low-E storms carried by box stores are decent enough- but noticeably more air-tight if you upgrade to at least the "Silver" series rather than the low-end "Bronze."
Good input Dana. I'll take a look at those storm windows. We are near an interstate so we have noise as well.those might work well
More info on low-E storms:
http://labhomes.pnnl.gov/documents/PNNL_23355_Lab_Homes_Low-e_Storms.pdf
^^probably more than you wanted ton know^^ The one line summary is that low E storms on the experimental house saves about 12% on the home's heating energy use, 8% on the cooling energy use in a US climate zone 5B climate (Richland, WA), with steadier mean radiant temps indoors (the primary factor for comfort.) See P 49 for the 1-pager. In TN it'll probably be comparable, perhaps better slightly cooling season savings in TN than in eastern WA due to the lower latitude/higher-sun.
http://energy.gov/energysaver/projects/savings-project-install-exterior-storm-windows-low-e-coating
http://low-estormwindows.com/about/